This invention relates in general to drums and more particularly to an improved drum head construction.
Modern drum heads are typically constructed of polyester films which are secured at their edges in various ways. As disclosed in U.S. Pat. No. 2,934,989 to Belli et al., the edge of the film may be inserted into a channel shaped metal hoop which is then filled with a resinous bonding material that bonds the head to the channel. Pins and various other mechanical fasteners have also been used either alone or together with a bonding substance.
Although this type of construction has long been used, it has not been wholly free of problems. A major difficulty that can lead to early failure of the drumhead results from the susceptibility of the resin to release from the hoop due to the sometimes considerable forces that are applied to the drumhead. Because of the simple channel shaped construction of the hoop, there is nothing but the bonding force between the resin and the hoop to hold the resin in place, and if the bonding force fails, the resin can simply slip out of the channel and release the margin of the drumhead. Another problem of the simple U-shaped channel is that it provides only a relatively small area for the counter hoop of the drum to bear against. The resin can also easily run out of the channel before it has hardened, thus creating unattractive "blobs" which can detract significantly from the appearance of the drum.
Another problem that can lead to early failure of the drumhead is created by the presentation of sharp edges on the retaining hoop which can contact the polyester film and cut or otherwise damage it. The joint between the two ends of the hoop has been a particularly serious source of problems. Typically, this joint creates a weak point of the drumhead which is reinforced by crimping a reinforcing strip onto the butting ends of the inside wall of the channel. Such crimped metal strips often fail to add enough strength to the joint to enable it to withstand the forces to which it is subjected in normal use. Moreover, a joint constructed in this manner can easily become misaligned and is unsightly in any event.